This invention relates to oral administration forms of potassium, and more particularly to controlled release tablets or capsules containing potassium chloride in a form which releases the drug gradually over a prolonged period of time after ingestion to protect the gastrointestinal tract from the irritation and toxicity accompanying high potassium ion concentrations.
Potassium is the principal intracellular cation in mammals. It is present in a concentration of approximately 140 meg/L inside the cell. The intracellular potassium may be lost over a period of time from various stressful and debilitating conditions including diuretic drug treatment. As the intracellular potassium is depleted, various cells, including heart muscle, become dysfunctional, eventually resulting in death. Various means are available for correcting potassium loss, including direct intravenous injection and oral dosage forms.
Ironically, the potassium ion is quite toxic outside the cell. It normally has a concentration of about five meg/L in extracellular fluids. Levels that are much greater stop cell function. If the required therapeutic dose is injected in concentrated form intravenously, it may kill the patient instantly. When it is administered orally as the potassium chloride salt, it may cause irritation, inflammation and erosion of the mucosal lining of the gastrointestinal tract.
A variety of oral dosage forms of potassium have been developed to provide long term potassium supplements that are less harmful to the user.
U.S. Pat. No. 4,863,743 issued Oct. 5, 1989 to Hsiao provides a review of the prior art of oral therapeutic potassium supplements and the problems they present. He discloses a controlled release tablet formed from potassium chloride crystals coated with a coating mixture of ethylcellulose and one member selected from hydroxypropylcellulose and polyethylene glycol and compressed into tablets with microcrystalline cellulose and crosslinked polyvinylpyrrolidone. He found that low viscosity ethylcellulose was not suitable because the particles broke up during compression. He therefor recommended the high viscosity material of 100 cp., and claims are limited to greater than 40 cp.
U.S. Pat. No. 5,035,898 issued Jul. 30, 1991 to Chang et al. discloses potassium chloride crystals coated with a combination of high viscosity ethylcellulose and at least one of hydroxypropylcellulose and polyethyleneglycol as taught by Hsiao along with a magnesium salt.